This invention relates to means for cooling the internal parts of electric motors and has particular reference to a substantially noiseless fan for internally cooling a high speed electric motor, such as used for driving small hand-held tools and the like.
Heretofore, fans for the internal cooling of high speed electric motors have generally comprised a rotating fan member carried by the motor shaft and having a plurality of radially extending fan blades which cause a flow of cooling air over the rotor and stator elements of the motor. The fan blades exert a shoving action against the air and at high speeds they tend to agitate or churn the air resulting in turbulence which causes an undesirable noise and reduces the air moving efficiency of the fan.